1. Field of the Invention
This invention relates to a keyboard device for a keyboard instrument, such as an electronic piano.
2. Description of the Prior Art
Conventionally, this kind of keyboard device has been proposed e.g. in Japanese Laid-Open Patent Publication (Kokai) No. 2000-122654. This keyboard device is for use in an electronic piano, and as shown in FIG. 15, it includes a chassis assembly 81, a plurality of keys 82 (only one of which is shown) and a plurality of hammers 83 (only one of which is shown). The chassis assembly 81 is comprised of six intermediate chassis 81a (see FIG. 16) each provided as a unit for one octave, a chassis (not shown) for the lowest pitch range, and a chassis (not shown) for the highest pitch range, which are formed by injection molding of a synthetic resin, such as an ABS resin. The intermediate chassis 81a are identical in size and shape. These eight chassis are connected by four connecting bars 91 extending in the left-right direction, such that they are arranged side by side in the left-right direction, and supported on a keybed 84. Each of the chassis has key supports 85 formed at a rear end thereof, hammer supports 86 formed at a central portion thereof, second hammer passage holes 87 formed through respective portions forward of the hammer supports 86, and first hammer passage holes 88 formed through a front end thereof (see FIG. 16). The key supports 85, the hammer supports 86, the second hammer passage holes 87, and the first hammer passage holes 88 are formed in association with the respective keys 82. Each adjacent two of the first hammer passage holes 88 are separated by a sidewall 90.
The keys 82 are comprised of white keys 82a and black keys 82b. Each of the keys 82 has a rear end thereof pivotally supported by the associated key support 85 of the chassis assembly 81, and extends in the front-rear direction on the upper side of the chassis assembly 81. Each hammer 83 also extends in the front-rear direction, and the rear end thereof is mounted to two adjacent hammer supports 86 and 86 in a manner spanning these, and pivotally supported by them. Further, the hammer 83 passes through the associated second hammer passage hole 87 and extends forward below the chassis assembly 81. The hammer 83 has weight plates 89 (only one of which is shown) attached to the respective left and right side surfaces of the front end thereof, for adding weight to the hammer 83. Above the front end of the hammer 83, there opens the associated first hammer passage hole 88.
Fixed to the four connecting bars 91 connecting the chassis are ribs 92 (only one of which is shown) for reinforcing the rigidity of the chassis assembly 81 in the front-rear direction, which are arranged at respective predetermined locations on an octave-by-octave basis in a manner spanning the connecting bars 91. The ribs 92 are each formed e.g. of a single steel plate, and extend below the associated sidewall 90 over substantially the entire length of the chassis assembly 81 in the front-rear direction such the ribs 92 do not come into contact with the hammers 83.
With the arrangement described above, as a key 82 is depressed, the rear end of the associated hammer 83 is pressed downward by the key 82, whereby the hammer 83 is pivoted clockwise, as viewed in FIG. 15, about the hammer supports 86. In accordance with the pivotal motion, the front end of the hammer 83 passes through the first hammer passage hole 88 from below.
In the above-described conventional keyboard device, the hammer 83 has the rear end thereof supported by the hammer supports 86, with the front end thereof being freely movable in the left-right direction. For this reason, when the electronic piano is stored in a vertically placed position in which the lateral sides thereof are turned into the respective top and bottom sides thereof, the hammer 83 largely hangs down from the hammer supports 86, and there acts large bending moment caused by the weight of the hammer itself including the weight plates 89 positioned remote from the hammer supports 86, so that there is a fear of the hammer 83 being deformed. If the hammer 83 is deformed, when the electronic piano is played in its horizontal or normal position, the hammer 83 passing through the first hammer passage hole 88 can come into contact with the sidewall 90 of the first hammer passage hole 88, thereby hindering the musical performance.
To eliminate the above-described inconvenience, a method can be contemplated in which the left and right sidewalls 90 of each first hammer passage hole 88 are extended downward, as shown in FIGS. 17 and 18, and fixed on the keybed 84, for example, for restriction of the lateral motion of the hammer 83. In this case however, as shown in FIG. 18, to make the distance between the respective adjacent first hammer passage holes 88 and 88 of the opposed boundary portions of the intermediate chassis 81a and 81a equal to the distance between those of the other portions, it is required to make the respective adjacent outermost sidewalls 90a and 90a of the two boundary portions thinner than those of the other portions, so that the strength of the sidewalls 90a and 90a is reduced. Further, since the outermost sidewalls 90a are thin and wider than the conventional ones, the sidewalls 90a and 90a are liable to undergo vibrations e.g. by contact with the associated hammers 83, which can cause undesired noise. To eliminate this inconvenience, if the intermediate chassis 81a and 81a are bonded to each other, this increases the number of manufacturing steps, which increases the manufacturing costs, and makes it difficult to disassemble the chassis assembly 81.
Further, since the sidewalls 90 are extended to the keybed 84, there is no space for arranging the ribs 92, and hence it is impossible to attach the ribs 92 to the chassis assembly 81. As a result, the rigidity of the chassis assembly 81 in the front-rear direction is reduced, so that there is a fear of the chassis assembly 81 being bent e.g. due to the weight of the hammers 83, thereby hindering a musical performance. To solve this problem, it can be considered that the ribs 92 or other reinforcing members are provided at locations other than the locations below the sidewalls 90 so as to reinforce the chassis assembly 81, but in this case, there is a problem of the keyboard device being inevitably increased in size.